Question

1)What details would an epidemiologist need to consider to determine the source of an infection

2) What is the difference between infection and intoxication as it pertains to foodborne illness? How do the symptoms vary?

3) Infection by E. coli O157:H7 may occur with only 10 CFU/mL. Which sample(s) would be of concern if the contaminated water contained strain O157:H7?
4) What are the symptoms of an intestinal infection caused by E. coli? How do the symptoms differ from an infection caused by the strain O157:H7?
5 ) If a “boil water advisory” is issued, how should you treat the water to make it drinkable? How long should water be boiled before it is considered safe?
6)  Once the boil water advisory is over, what advice is given to make the water drinkable and to make sure your household is safe?

Answer 1

1)By reviewing and plotting on an "epidemic curve" the times of onset of the cases and by examining the characteristics (e.g., age, sex, race/ethnicity, residence, occupation, recent travel, or attendance at events) of the ill persons, investigators canoften generate hypotheses concerning the cause(s)/source(s) of infection.

2)

Diseases which result from pathogenic microorganisms are of two types: infection and intoxication.

• Foodborne infection is caused by the ingestion of food containing live bacteria which grow and establish themselves in the human intestinal tract.
• Foodborne intoxication is caused by ingesting food containing toxins formed by bacteria which resulted from the bacterial growth in the food item. The live microorganism does not have to be consumed.

For a foodborne illness(poisoning) to occur, the following conditions must be present:

• The microorganism or its toxin must be present in food.
• The food must be suitable for the microorganism
  to grow.
• The temperature must be suitable for the microorganism
  to grow.
• Enough time must be given for the microorganism
  to grow (and to produce a toxin).
• The food must be eaten.

Symptoms of Foodborne Illness

The most common symptom associated with foodborne illnesses is diarrhea. Each pathogenic microorganism has its set of characteristic symptoms.

The severity of the foodborne illness depends on the pathogenic microorganism or toxin ingested, the amount of food consumed (dose), and the health status of the individual. For individuals who have immunocompromised health conditions, or for the aged, children, or pregnant women, any foodborne illness may be life-threatening.

3)

E. coli O157:H7 is most commonly found on a small number of cattle farms where the bacteria can live in the intestines of healthy cattle. Millions of germs can be released in a bowel movement from an infected human or animal. E. coli O157:H7 may be found in water sources, such as private wells, that have been contaminated with feces from infected humans or animals. Waste can enter the water through different ways, including sewage overflows, sewage systems that are not working properly, polluted storm water runoff, and agricultural runoff. Wells may be more vulnerable to such contamination after flooding, particularly if the wells are shallow, have been dug or bored, or have been submerged by floodwater for long periods of time.

4)

Symptoms of intestinal infection due to E. coli

• abdominal cramping.
• sudden, severe watery diarrhea that may change to bloody stools.
• gas.
• loss of appetite or nausea.
• vomiting (uncommon)
• fatigue.
• fever.

whereas Ecoli O157:H7 can develop a variety of symptoms, but they most often include stomach cramping, diarrhea (often bloody), and vomiting. Fever is not usually present. In some cases, those infected experience only mild diarrhea or no symptoms at all. For others, illness can become severe or even fatal.

5)Boiling is sufficient to kill pathogenic bacteria, viruses and protozoa (WHO, 2015). If water is cloudy, let it settle and filter it through a clean cloth, paperboiling water towel, or coffee filter. Bring water to a rolling boil for at least one minute.

6)In most cases, it is safe to wash your hands with soap and tap water during a Boil Water Advisory. Follow the guidance from your local public health officials. If soap and water are not available, use an alcohol-based hand sanitizer containing at least 60% alcohol.